As individuals age, their spinal discs tend to degenerate over time. This can result in a decrease in the disc space height. In addition, the facets and ligaments of the spine degenerate as well over time. These problems can lead to a reduction in the foramenal height of the vertebrae. The foramen is a natural opening between the vertebrae that allows the passage of respective nerves from the spinal cord. Because the nerves pass through the respective foramen, a reduction in the foramenal height may often causes nerve tissue to get pinched leading to various types of back pain. These pinched or compressed nerves can also lead to difficulty in walking.
Surgical solutions to this problem require the surgical removal of the ligaments and bone that are causing the compression. A number of interspinous process devices have been designed to act as spacers to flex the spine and open the canal, lateral recess and foramen to take pressure off of the compressed or pinched nerves. Designs vary from static spacers to dynamic, spring-like devices. These may be made from bone allograft, titanium, polyetheretherketone (PEEK), and elastomeric compounds. The common goal between these devices is to mechanically distract the spinous processes and blocking extension (of the abdominal muscles) that affect the intervertebral relationship. Examples of these include the X STOP device (Medtronic, Memphis, Tenn.), ExtenSure device (NuVasive, San Diego, Calif.), and the Wallis system (Abbott Spine, Bordeaux, France). Often, these devices are successful in alleviating symptoms of patients post surgery, however, many patients have recurring symptoms after months or years have passed.